1. Field of the Invention
This invention relates to train handling apparatus and more particularly to apparatus for holding the cars in place on the track and for relieving the load imposed by the cars on the apparatus during disengagement.
2. Prior Art
Bulk material carrying trains are typically loaded and unloaded by cycling the cars, either singly or up to several at a time, through work stations designed for efficient, high-speed load transfer operations. It is common practice to utilize specialized car handling equipment to index the cars through the work stations, both to expedite load transfer and to avoid tying up a locomotive. U.S. Pat. No. 4,006,691, for example, discloses car handling apparatus which indexes cars through a rotary car dumper using a car positioner which moves along its own set of tracks parallel to the railroad track and has an arm which reaches between the cars to engage the car couplings. The apparatus disclosed in this patent also includes a train holding device which engages the couplings between cars to hold them against forces resulting from track gradient, etc. while the car positioner disengages and repositions for another indexing stroke. This car holding device includes a base mounted alongside the track and an arm mounted on the base for pivotal movement in a vertical plane between the car holding and a retracted position. The arm can move a limited distance along its pivot axis parallel to the track to transfer impact loading between the cars to shock absorbers. Although not shown in the patent, installed units have a camming mechanism which recenters the arm as it is retracted. However, this prior art arm is not provided with its own mechanism for initiating movement parallel to the track while in engagement with the train. Consequently, the train positioner must be used to accurately locate the railroad car couplers adjacent the holding arm so that it can engage and disengage under no-load conditions. Since the positioner may be several car lengths away from the holding arm and since the positioner must move very slowly during these operations, several seconds may be required for such positioning. The cumulative effect of such delays in detrimental to the overall capacity of the dumper station.